Rickettsia Flashcards
What causes rickettsia
Rickettsiaceae
What do rickettsia genus cause
Spotted fever
Typhus fever
Scrub typus
Causes of spotted fever
Rickettsia rickettsii (rocky mountain) - orth america
Rickettsia akrai (boutonneuse fever)
Rickettsia sibricia , australis felis - flea, japnoica, africae
African tick bite fever
Typhus group of rickettsiae causative organsims
Rickettsia prowazekii - epidemic typhus, recrudescent typhus, sporadic typhus
Rickettsia typhi - murine typhus (endemic typhus)
Scrub typhus group causative organisms
Rickettsia tsutsuganmushi
What is scrub typhus
Acute febrile infectious disease caused by orientia tsutsugamushi
Symptoms of rickettsia
Eschar
Regional lymphadenopathy
Fever
Maculopapular rash
Leukopenia
What is o.tsutsugamushi sensitive to
Chloramphenicol and tetracycline
Source of infection and transmission of rickettsia
Rat -> trombiculid mites
Transmitted to humans by arthropods - ticks, mice, louse, flease
Larva of trombiculid mite
Spread by haematogenous or lymphatics
Immunity to serotypes once have rickettsia
Only to that serotype - no protection from others
What is the tsutsugamushi traingale
Geographical area where ecposed to rickettsia -
Northern japan and far eastern russia
to northern australia to pakistan and afghanistan
Jungle, scrub and grassland
Seasonal peaks in north vs sotuh
South - may to cotober with maximal peak june to july
North - septmeber to december w maximal peak in october
Features of o.tsutsugamushi bacteria
Obligate intracellular parasites
Gram negative coccobacilli
RNA and DNA (binary fission_
Stains red on giemsa or gimenez stain
What colour does o.tsutsugamushi stain on giemsa or gimenez stian
Red
Pathogenesis of rickettsia
Maculopapular rash, eschar, ulcer
Enlargement of local ly,ph node -> blood
General symptoms sepsis -> generalised hyperaemia, systemic lymphadenopath
INcubation period of rickettsia
4-21 days
Presentation of firs week of ricketttsia
Sudden onset of fecer - systemic toxic symptoms
2nd week vs 3rd week of rickettsia
3rd week - Worse, complications, 4th week convalesce
What is eschar
Ulcer surrounded by red arcola often overed by dark scab
Most common areas for eschar location
Axillary fossa, inguinal region, perianal region, scortum, buttocks, thigh
What is most specific manifestation of scrub typhus
Eschar
Specific features of rickettsia
Eschar
Maculopapular rases (end of first week, chest, abdo, trunk, upper or lower limbs)
Local lymphadenopathy
Haematology/biochemical markers of rickettsia
Leukopenia
Normal WCC
Elevated w complications
Injury of liver function, CRP
What test for rickettsia
weil-felix test (esp in healthcare restricted settings)
How early can weil felix be psotivie
4th day after onset
What is diagnostic from weil-felix test
> 1:160 or increase 4 fold during course
Poor specialisation
What is gold standard tests for rickettsia
Indirect fluroescent antibody - IFA -
IIP - indirect immunosperoxidase test
When can IFA for rickettsia be postive from
positive from end of first week
Lasts for years
Pathogenic examination for rickettsia
Culture - use in mouse
Spleen and liver biopsy - stain with giemsa
PCR - orientia DNA
Not routinely available
Early course pathology of rickettsia
Perivascular lymphohistiocytic infiltrate and extravasated erythrocytes and dermal oedema
Dermal and epidermal necoriss later
positive r.rickettsiae imunohistochemical stain
Criteria for diagnosis of rickettsia
Visit endemic area last 3 weeks - work ,camp, grass sit
Clinical manifestation
Lab exam - weil feliz reaction
Differential diangoses rickettsia
Epidemic typhus - winter and spring louse bite, weil-felix and OX19 +
Typhus
Leptospirosis
Dengue
Kawasaki
Malaria
MEasles
Meningococcal
Rubella
Strep A
Syphilis
Toxic shock syndrome
Vasculitis, thrombophlebitis
Typhus features
slow onset fever. Confusion, bradycardia, digestive symtpoms, rose rash, no eschar, widal test positive
+ culutre of typhus bacilus positive
Leptospirosis how differntiate
Calf muscle tenderness
Microscopic haematuria
General treatment
IV fluids supportive
Intensive nursing care and prevent complication
Sensitive antibitics - mortality drastically reduced
Treatment regimes for rickettsia
Chloramphenicol - 2g/day (25mg/kg child)
Doxycycline - 0.2g/day adult (tetracycline alt)
Azithromycin 500mg daily
Roxithromycin - 0.6g/day adult - 2-3mg/kg/day child ESP in child useful
Treatment if resistnat rickettsia strain
Combination therapy doxycycline and rifampacin
Azithromycin
